[Extensions] Handle some funny cases in script injection

extensions/renderer/programmatic_script_injector.cc

Index: extensions/renderer/programmatic_script_injector.cc
diff --git a/extensions/renderer/programmatic_script_injector.cc b/extensions/renderer/programmatic_script_injector.cc
index bc94d043b27c9b756061ec694b95e1c9af7e45de..183ef54cbb6f7253b7be18bf2469a273a79c1dbc 100644
--- a/extensions/renderer/programmatic_script_injector.cc
+++ b/extensions/renderer/programmatic_script_injector.cc
@@ -9,6 +9,7 @@
 #include "base/values.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/renderer/render_frame.h"
+#include "content/public/renderer/render_frame_observer.h"
 #include "extensions/common/error_utils.h"
 #include "extensions/common/extension_messages.h"
 #include "extensions/common/manifest_constants.h"
@@ -22,13 +23,31 @@
 
 namespace extensions {
 
+class ProgrammaticScriptInjector::FrameWatcher

[not at google - send to devlin, 2015/06/29 18:28:11]

// Watches for the deletion of a RenderFrame, after which is_valid will return
false.

[Devlin, 2015/06/29 19:41:44]

Done.

+    : public content::RenderFrameObserver {
+ public:
+  explicit FrameWatcher(content::RenderFrame* render_frame)
+      : content::RenderFrameObserver(render_frame), is_valid_(true) {}
+  ~FrameWatcher() override {}
+
+  bool is_frame_valid() const { return is_valid_; }
+
+ private:
+  void FrameDetached() override { is_valid_ = false; }
+  void OnDestruct() override { is_valid_ = false; }
+
+  bool is_valid_;
+
+  DISALLOW_COPY_AND_ASSIGN(FrameWatcher);
+};
+
 ProgrammaticScriptInjector::ProgrammaticScriptInjector(
     const ExtensionMsg_ExecuteCode_Params& params,
     content::RenderFrame* render_frame)
     : params_(new ExtensionMsg_ExecuteCode_Params(params)),
-      url_(ScriptContext::GetDataSourceURLForFrame(
-          render_frame->GetWebFrame())),
-      render_frame_(render_frame),
+      url_(
+          ScriptContext::GetDataSourceURLForFrame(render_frame->GetWebFrame())),
+      frame_watcher_(new FrameWatcher(render_frame)),
       finished_(false) {
   effective_url_ = ScriptContext::GetEffectiveDocumentURL(
       render_frame->GetWebFrame(), url_, params.match_about_blank);
@@ -150,12 +169,15 @@ void ProgrammaticScriptInjector::Finish(const std::string& error) {
   DCHECK(!finished_);
   finished_ = true;
 
-  render_frame_->Send(new ExtensionHostMsg_ExecuteCodeFinished(
-      render_frame_->GetRoutingID(),
-      params_->request_id,
-      error,
-      url_,
-      results_));
+  // It's possible that the render frame was destroyed in the course of
+  // injecting scripts. Don't respond if it was (the browser side watches for
+  // frame deletions so nothing is left hanging).
+  if (frame_watcher_->is_frame_valid()) {
+    frame_watcher_->render_frame()->Send(
+        new ExtensionHostMsg_ExecuteCodeFinished(
+            frame_watcher_->render_frame()->GetRoutingID(), params_->request_id,
+            error, url_, results_));
+  }
 }
 
 }  // namespace extensions